What type of ‘crea­tures’ are pathogens?

EBOLA, bird ‘flu, SARS, swine ‘flu, AIDS, the common cold, in­fluenza, po­lio, chick­en­pox, measles, mumps and a host of other common dis­eases are caused by viruses so we are well fa­mil­iar with th­ese pathogens but what kind of ‘crea­tures’ are they?

De­bate con­tin­ues as to where the thou­sands of viruses that have been iden­ti­fied be­long in the great scheme of things. Some au­thor­i­ties main­tain they are prim­i­tive life forms. Oth­ers dis­pute that they are alive at all and clas­sify them as non-liv­ing ‘par­ti­cles’, ‘agents’ or ‘en­ti­ties’ that went down an evo­lu­tion­ary cul-de-sac in the very early days of the de­vel­op­ment of life on Earth.

While viruses ap­pear to be alive in that they can grow, have genes and can re­pro­duce, they are in­ca­pable of sur­viv­ing on their own. They need a host to support them. They failed to evolve a cel­lu­lar struc­ture of their own and need to get inside the cells of a host plant or an­i­mal to sur­vive. If they end up out­side the bod­ies of plants and an­i­mals for a pro­longed pe­riod of time they die.

To say they failed to de­velop a cell struc­ture may be a neg­a­tive way of per­ceiv­ing them. The al­ter­na­tive per­cep­tion is that they suc­ceeded in evolv­ing to in­fil­trate the bod­ies of other life forms in­clud­ing bac­te­ria thereby en­sur­ing their sur­vival.

Fos­sil viruses have never been found so their ori­gin is un­clear. They have very sim­ple bod­ies and are ca­pa­ble of mu­tat­ing or un­der­go­ing change very rapidly so the strain of virus that presents it­self this year may not be the same strain as that of its an­ces­tors that pre­sented last year or five years ago.

And to add to that cock­tail of com­pli­cat­ing fac­tors they are ex­tremely tiny in size: the typ­i­cal virus is about 45,000 times smaller than the width of a hu­man hair. How­ever, what they lack in size they make up for in num­bers; viruses are the most abun­dant biological en­ti­ties on Earth in terms of ab­so­lute num­bers.

Many viruses dam­age their hosts to the point of caus­ing death and so they must move on to find a new host. We are all too fa­mil­iar with the sights on TV of peo­ple clad in PPE cov­er­all suits in west Africa bury­ing vic­tims of the deadly Ebola virus while try­ing to pro­tect them­selves from in­fec­tion and stop the spread of th­ese ex­tremely tiny but ex­tremely dan­ger­ous pathogens be they crea­tures, par­ti­cles, agents, en­ti­ties or what­ever.

The ‘flu virus has a strik­ing body shape with spikes of pro­teins and sug­ars aris­ing from a spher­i­cal en­ve­lope of fat.